Reciprocating piston type compressors typically employ suction and discharge pressure actuated valving mounted onto a valve plate assembly which is located at the end of a cylinder formed by a compressor body. The valve plate assembly is typically sandwiched between a compressor head and the compressor body. A valve plate gasket is located between the valve plate assembly and the compressor body to seal the interface.
Traditionally, the valve plate gasket is compressed due to a clamping load which is created by the attachment of the compressor head to the compressor body. The compressor head is attached to the compressor body by head bolts which extend through the compressor head, through the head gasket, through the valve plate assembly through the valve plate gasket and finally threadingly received by the compressor body. As these head bolts are tightened, compression of the valve plate gasket occurs.
Typically, the head bolts are located around the outside perimeter of the compressor head, the valve plate assembly and the valve plate gasket. Thus, the valve plate gasket receives most of its clamping load from this outside perimeter. Because the clamping load is generated at the outside perimeter of the valve plate gasket, there is a lower clamping load and thus a lower amount of compression of the valve plate gasket in the center portion of the valve plate gasket spaced from the outside perimeter. Because of this lower amount of compression of the valve plate gasket in the center portion, most of the valve plate gasket failures occur in this center portion.
In addition to compression of the valve plate gasket by the head bolts, valve plate gasket compression load is also created by the high pressure discharge gas located above the valve plate assembly. This high pressure discharge gas presses the valve plate assembly against the valve plate gasket and the compressor body. Typically the valve plate assembly is comprised of an upper valve plate, a lower valve plate and one or more spacers located between the upper and lower valve plates. In the center area of the valve plate assembly, there is no head bolt as described above and thus there is no spacer which creates an open void due to the lack of a spacer between the upper and lower valve plates. This means that the load, exerted by the high pressure discharge gas, is exerted on the upper valve plate and this exerted pressure is not transmitted directly to the lower valve plate in this center portion.
The present invention provides the art with a unique valve plate assembly which improves the valve gasket clamping load in the center portion and thus it significantly reduces valve gasket failures. The unique valve plate assembly of the present invention includes a center spacer which is located between the upper and lower valve plates in the center portion of the valve plate assembly. By incorporating this additional center spacer, the valve plate assembly exerts an increased clamping force in this center portion to increase the compression of the valve plate gasket and thus improve its performance and durability.
In the first embodiment of the present invention, the center spacer defines a bolt hole which extends through the spacer. A center bolt is assembled through the valve plate assembly using this bolt hole and it is threadingly received by the compressor body. When this center bolt is tightened, it provides additional clamping load to the valve plate gasket in the center portion to produce a more even clamping load throughout the entire valve plate gasket to improve performance and durability while reducing failures. The center bolt can extend only through the valve plate assembly and through the valve plate gasket into the compressor body or the center bolt can extend through the compressor head, through the valve plate assembly and through the valve plate gasket into the compressor body if desired.
In another embodiment of the present invention, the center spacer does not include the bolt hole. The center spacer is located within the center portion of the valve plate assembly to transmit both the clamping load and the pressure exerted by the high pressure discharge gas from the upper valve plate, to the lower valve plate, to the valve plate gasket and finally to the compressor body. This additional load exerted onto the valve plate gasket at its center portion increases the compression of the gasket at the center portion to produce a more even clamping load throughout the entire valve plate gasket to improve performance and durability while reducing failures. This additional embodiment is useful when it is not possible to assemble a center bolt due to a compressor unloader system or other features of the compressor being located at a position which limits access to the center portion of the valve plate assembly.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.